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W02D01 - TDD, CommonJS, and NPM

To Do

  • Manual testing
  • Making assertions
  • Bringing in outside code
  • Exporting our code
  • Intro to NPM: a Node package manager
  • Mocha test runner
  • Ignoring files/folders
  • Chai assertion library
  • What is TDD?
  • Practice unit testing

TDD

  • Test Driven Development
  • Tests are written before the code is written
  • We use a process called Red-Green-Refactor
  • Red: The test is failing
  • Green: The test is passing
  • Refactor: Improve the existing code safe in the knowledge that the functionality is testable
  • BDD: Behaviour Driven Development
    • Very similar to TDD, but the focus is more on the end user rather than the quality of the code under test

Mocha

  • A testing framework
  • By default, looks in the test folder for test files to run

Chai

  • An assertion library
  • We can use assertions to describe the desired outcome of our code
  • Chai offers three different interfaces: should, expect, and assert
  • For most uses, choosing which interface to use is a matter of preference
// should
myVar.should.be.a('string');
myVar.should.equal('hello world');

// expect
expect(myVar).to.be.a('string');
expect(myVar).to.equal('hello world');

// assert
assert.typeOf(myVar, 'string');
assert.equal(myVar, 'hello world');

module.exports and require

  • We can export functions, objects, etc from a file using the module.exports object
  • You can add new keys to the module.exports object or you can completely overwrite it with a function/object
// adding new keys to module.exports
module.exports.myFunc = myFunc;
module.exports.myOtherFunc = myOtherFunc;

// overwriting module.exports object
module.exports = myFunc;
// or
module.exports = {
  myFunc,
  myOtherFunc
};
  • As you have previously seen, we can bring functions, objects, etc into a file using require
// basic require syntax
const myFunc = require('./myFunc');

// if the file exports an object, we can use ES6 destructuring
const { myFunc } = require('./myFunc');

Ignoring files/folders

  • Sometimes there are files or folders that we do not want git to track for us
  • These files might contain sensitive information such as passwords or API keys
  • They might also be folders such as node_modules which should always be ignored
  • We can tell git to ignore certain files/folders by using a special file called .gitignore (note the leading period)
  • Any files that we specify inside of .gitignore will be ignored by git
# inside .gitignore
node_modules
my-file.js
  • Using the above file, the node_modules folder and the file my-file.js will not be tracked by git

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